This invention relates to photodetecting fibers and more particularly to fibers including a resistive channel that breaks the fiber axial symmetry enabling the imposition of non-uniform, convex electric potential distributions along the fiber axis to detect and localize an incident optical beam.
Optical fibers rely on translational axial symmetry to enable long distance transmission. Their utility as a distributed sensing medium [1-3] relies on axial symmetry breaking either through the introduction of an a priori axial perturbation in the form of a bragg grating [4], or through the use of optical time (or frequency) domain reflectometry techniques [5,6] which measure scattering from an adhoc axial inhomogeneity induced by the incident excitation. These have enabled the identification and localization of small fluctuations of various stimuli such as temperature [7-9] and stress [10-11] along the fiber axis. Due to the inert properties of the silica material, most excitations that could be detected were the ones that led to structural changes, importantly excluding the detection of radiation at optical frequencies. Recently, a variety of approaches have been employed, aimed at incorporating a broader range of materials into fibers. [12-20]. In particular, multimaterial fibers with metallic and semiconductor domains have presented the possibility of increasing the number of detectable excitations to photons and phonons [19-25] over unprecedented length and surface area. Several applications have been proposed for these fiber devices in imaging [23,24], industrial monitoring [26,27], remote sensing and functional fabrics [20,21].
So far however, the challenges associated with resolving the intensity distribution of optical excitations along the fiber axis have not been addressed. Here we propose an approach that allows extraction of axially resolved information in a fiber that is uniform along its length without necessitating fast electronics or complex detection architectures.